9) Two mirrors are at right angles to one another. A light ray is incident on the first at an angle of 30° with respect to the normal to the surface. What is the angle of reflection from the second surface?

60°

Explanation:

In the given question it is given that the two mirrors perpendicular to each other.

The light ray will reflect off the first mirror with an angle of 30° (∠i = ∠r) and then arrive at the second mirror. Using geometry of the two mirrors and the fact that the angle between the two of them is 90°, the incident angle for second mirror is 60°, which will again equal to the angle of reflection.

hence, angle of reflection of second mirror is 60°